metadata: split context to incoming and outgoing

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

metadata/context.go

@@ -5,35 +5,64 @@ import (
 	"context"
 )
 
+type mdIncomingKey struct{}
+type mdOutgoingKey struct{}
+type mdKey struct{}
+
+// FromIncomingContext returns metadata from incoming ctx
+// returned metadata shoud not be modified or race condition happens
+func FromIncomingContext(ctx context.Context) (Metadata, bool) {
+	if ctx == nil {
+		return nil, false
+	}
+	md, ok := ctx.Value(mdIncomingKey{}).(Metadata)
+	return md, ok
+}
+
+// FromOutgoingContext returns metadata from outgoing ctx
+// returned metadata shoud not be modified or race condition happens
+func FromOutgoingContext(ctx context.Context) (Metadata, bool) {
+	if ctx == nil {
+		return nil, false
+	}
+	md, ok := ctx.Value(mdOutgoingKey{}).(Metadata)
+	return md, ok
+}
+
 // FromContext returns metadata from the given context
+// returned metadata shoud not be modified or race condition happens
+//
+// Deprecated: use FromIncomingContext or FromOutgoingContext
 func FromContext(ctx context.Context) (Metadata, bool) {
 	if ctx == nil {
 		return nil, false
 	}
-	md, ok := ctx.Value(metadataKey{}).(Metadata)
-	if !ok {
-		return nil, ok
-	}
-	nmd := Copy(md)
-	return nmd, ok
+	md, ok := ctx.Value(mdKey{}).(Metadata)
+	return md, ok
 }
 
 // NewContext creates a new context with the given metadata
+//
+// Deprecated: use NewIncomingContext or NewOutgoingContext
 func NewContext(ctx context.Context, md Metadata) context.Context {
 	if ctx == nil {
 		ctx = context.Background()
 	}
-	return context.WithValue(ctx, metadataKey{}, Copy(md))
+	return context.WithValue(ctx, mdKey{}, md)
 }
 
-// MergeContext merges metadata to existing metadata, overwriting if specified
-func MergeContext(ctx context.Context, pmd Metadata, overwrite bool) context.Context {
+// NewIncomingContext creates a new context with incoming metadata attached
+func NewIncomingContext(ctx context.Context, md Metadata) context.Context {
 	if ctx == nil {
 		ctx = context.Background()
 	}
-	md, ok := FromContext(ctx)
-	if !ok {
-		return context.WithValue(ctx, metadataKey{}, Copy(pmd))
-	}
-	return context.WithValue(ctx, metadataKey{}, Merge(md, pmd, overwrite))
+	return context.WithValue(ctx, mdIncomingKey{}, md)
+}
+
+// NewOutgoingContext creates a new context with outcoming metadata attached
+func NewOutgoingContext(ctx context.Context, md Metadata) context.Context {
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	return context.WithValue(ctx, mdOutgoingKey{}, md)
 }

metadata/metadata.go

@@ -2,7 +2,6 @@
 package metadata
 
 import (
-	"context"
 	"net/textproto"
 	"sort"
 )
@@ -12,16 +11,14 @@ var (
 	HeaderPrefix = "Micro-"
 )
 
-type metadataKey struct{}
-
 // Metadata is our way of representing request headers internally.
 // They're used at the RPC level and translate back and forth
 // from Transport headers.
 type Metadata map[string]string
 
 var (
-	// DefaultMetadataSize used when need to init new Metadata
-	DefaultMetadataSize = 6
+	// defaultMetadataSize used when need to init new Metadata
+	defaultMetadataSize = 2
 )
 
 type Iterator struct {
@@ -72,12 +69,9 @@ func (md Metadata) Set(key, val string) {
 // Del is used to remove value from metadata
 func (md Metadata) Del(key string) {
 	// fast path
-	if _, ok := md[key]; ok {
-		delete(md, key)
-	} else {
-		// slow path
-		delete(md, textproto.CanonicalMIMEHeaderKey(key))
-	}
+	delete(md, key)
+	// slow path
+	delete(md, textproto.CanonicalMIMEHeaderKey(key))
 }
 
 // Copy makes a copy of the metadata
@@ -89,39 +83,10 @@ func Copy(md Metadata) Metadata {
 	return nmd
 }
 
-// Del deletes key from metadata
-func Del(ctx context.Context, key string) context.Context {
-	md, ok := FromContext(ctx)
-	if !ok {
-		md = New(0)
-	}
-	md.Del(key)
-	return context.WithValue(ctx, metadataKey{}, md)
-}
-
-// Set add key with val to metadata
-func Set(ctx context.Context, key, val string) context.Context {
-	md, ok := FromContext(ctx)
-	if !ok {
-		md = New(0)
-	}
-	md.Set(key, val)
-	return context.WithValue(ctx, metadataKey{}, md)
-}
-
-// Get returns a single value from metadata in the context
-func Get(ctx context.Context, key string) (string, bool) {
-	md, ok := FromContext(ctx)
-	if !ok {
-		return "", ok
-	}
-	return md.Get(key)
-}
-
 // New return new sized metadata
 func New(size int) Metadata {
 	if size == 0 {
-		size = DefaultMetadataSize
+		size = defaultMetadataSize
 	}
 	return make(Metadata, size)
 }

metadata/metadata_test.go

@@ -2,8 +2,6 @@ package metadata
 
 import (
 	"context"
-	"fmt"
-	"reflect"
 	"testing"
 )
 
@@ -32,26 +30,27 @@ func TestIterator(t *testing.T) {
 	var k, v string
 
 	for iter.Next(&k, &v) {
-		fmt.Printf("k: %s, v: %s\n", k, v)
+		//fmt.Printf("k: %s, v: %s\n", k, v)
 	}
 }
 
 func TestMedataCanonicalKey(t *testing.T) {
-	ctx := Set(context.TODO(), "x-request-id", "12345")
-	v, ok := Get(ctx, "x-request-id")
+	md := New(1)
+	md.Set("x-request-id", "12345")
+	v, ok := md.Get("x-request-id")
 	if !ok {
 		t.Fatalf("failed to get x-request-id")
 	} else if v != "12345" {
 		t.Fatalf("invalid metadata value: %s != %s", "12345", v)
 	}
 
-	v, ok = Get(ctx, "X-Request-Id")
+	v, ok = md.Get("X-Request-Id")
 	if !ok {
 		t.Fatalf("failed to get x-request-id")
 	} else if v != "12345" {
 		t.Fatalf("invalid metadata value: %s != %s", "12345", v)
 	}
-	v, ok = Get(ctx, "X-Request-ID")
+	v, ok = md.Get("X-Request-ID")
 	if !ok {
 		t.Fatalf("failed to get x-request-id")
 	} else if v != "12345" {
@@ -61,9 +60,11 @@ func TestMedataCanonicalKey(t *testing.T) {
 }
 
 func TestMetadataSet(t *testing.T) {
-	ctx := Set(context.TODO(), "Key", "val")
+	md := New(1)
 
-	val, ok := Get(ctx, "Key")
+	md.Set("Key", "val")
+
+	val, ok := md.Get("Key")
 	if !ok {
 		t.Fatal("key Key not found")
 	}
@@ -78,15 +79,8 @@ func TestMetadataDelete(t *testing.T) {
 		"Baz": "empty",
 	}
 
-	ctx := NewContext(context.TODO(), md)
-	ctx = Del(ctx, "Baz")
-
-	emd, ok := FromContext(ctx)
-	if !ok {
-		t.Fatal("key Key not found")
-	}
-
-	_, ok = emd["Baz"]
+	md.Del("Baz")
+	_, ok := md.Get("Baz")
 	if ok {
 		t.Fatal("key Baz not deleted")
 	}
@@ -137,42 +131,3 @@ func TestMetadataContext(t *testing.T) {
 		t.Errorf("Expected metadata length 1 got %d", i)
 	}
 }
-
-func TestMergeContext(t *testing.T) {
-	type args struct {
-		existing  Metadata
-		append    Metadata
-		overwrite bool
-	}
-	tests := []struct {
-		name string
-		args args
-		want Metadata
-	}{
-		{
-			name: "matching key, overwrite false",
-			args: args{
-				existing:  Metadata{"Foo": "bar", "Sumo": "demo"},
-				append:    Metadata{"Sumo": "demo2"},
-				overwrite: false,
-			},
-			want: Metadata{"Foo": "bar", "Sumo": "demo"},
-		},
-		{
-			name: "matching key, overwrite true",
-			args: args{
-				existing:  Metadata{"Foo": "bar", "Sumo": "demo"},
-				append:    Metadata{"Sumo": "demo2"},
-				overwrite: true,
-			},
-			want: Metadata{"Foo": "bar", "Sumo": "demo2"},
-		},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			if got, _ := FromContext(MergeContext(NewContext(context.TODO(), tt.args.existing), tt.args.append, tt.args.overwrite)); !reflect.DeepEqual(got, tt.want) {
-				t.Errorf("MergeContext() = %v, want %v", got, tt.want)
-			}
-		})
-	}
-}